NASA's Orion Crew Exploration Vehicle (CEV) is designed to carry a crew and payload to Earth orbit and beyond. The CEV includes a capsule for holding a crew, a service module, and a booster for lift-off into Earth orbit.
The CEV capsule has an ablative aft heat shield for protecting the crew from extreme heat during re-entry into Earth's atmosphere. The heat shield is formed from heat-absorbing elements that are bonded to a structural substrate. The heat-absorbing elements are separated by a gap having a nominal thickness of 0.080±0.020 inches. The gaps are filled with a thixotropic sealant to prevent hot gases from reaching the capsule skin during re-entry. The current CEV heat shield has about 3000 inches of gaps to be filled.
During construction of a thermal protection system (TPS) manufacturing demonstration unit (MDU), a steel metal syringe needle was used to inject sealant into the gaps. The needle was attached to a pneumatic extrusion gun, which utilized polypropylene tubes filled with sealant. The extrusion gun was charged with (pressurized) plant air, the needle was inserted into a gap, and the extrusion gun injected the sealant through the needle and into the gap.
Filling all 3000 inches is a very slow process. The orifice opening of the needle restricts the flow and volume of the sealant into the gaps. An 18 gage syringe needle has been found to dispense the sealant at a rate of about 0.4 inches per minute. An 18 gage syringe needle has been found to take about 105 minutes to fill a 42 inch long gap having a nominal width of 0.080 inches and a nominal depth of about 4.2 inches. Filling all 3000 inches of gaps can take over 7500 minutes.
This slow process can affect a production schedule. And since the gaps are filled by manual labor, extra time filling the gaps can add to production costs.
It would be beneficial to increase the speed of filling and/or sealing the gaps with sealant.